In conventional technology, as shown in Japanese Patent Laid-open No. 2002-266688, ignition timing is delayed to execute the catalyst quick light-off at the cold start-up and the ISC gate opening is made larger than usual. When the shift range moves to the D range, the ignition timing is moved to the normal side, and associated torque fluctuation is to be absorbed by reducing the ISC gate opening so as to reduce the volume of intake air.
In another conventional technology, as shown in Japanese Patent Laid-open No. Hei 10(1998)-169434, oxygen is supplied through a secondary air inlet provided on an exhaust pipe until the catalyst is activated.